特旱条件下玉米自交系抗旱性评价

为了发掘和利用玉米抗旱种质资源,选育耐旱高产的玉米杂交种,通过全生育期控水试验,对58个玉米优良自交系的抗旱性进行了鉴定和评价,并进行了抗旱性聚类和遗传背景分析。结果表明：在特旱条件下,58个自交系减产幅度为40.6%-100%,平均产量下降了81.6%;结实率、穗行数、行粒数、出籽率4个性状分别与抗旱系数或抗旱指数存在显著或极显著的相关性,可作为玉米自交系抗旱性评价的关键指标;根据抗旱性的不同,58个自交系可划分为3类,其中第I类自交系K12、PB1139、RD6的抗旱性极强,第II类自交系CL11、郑58、P138、特早熟、Ft45-5具有较强的抗旱潜力。为了便于利用杂种优势,将不同抗旱性的自交系按照其所属遗传类群进行了再次划分,58个自交系可划分为2个类群,其中A群中抗旱性强的自交系有CL11和郑58,B群中抗旱性强的自交系有K12、PB1139、RD6、Ft45-5、P138和特早熟。

特旱特涝年气候对棉花产量及发育的影响

本文采用陕西关中东部1971-2000年30年棉花生长季节4-10月的降水资料,对历史上影响范围最大,强度最强的1997年和1983年棉花产量及发育状况进行分析。结果表明:特旱年份,棉花产量整体呈减产趋势,特旱年棉花早衰明显而普遍,座桃难、脱落多,水旱地差异显著;特涝年份总体上棉花是减产的。特涝年秋季连阴雨导致高湿、寡照、棉田湿度大,铃病易于流行,使棉桃霉烂、脱落、僵瓣多、铃重降低,影响产量。

雷州半岛特旱蔗区抗旱增产综合技术研讨

本文论述了雷州半岛特旱蔗区甘蔗抗旱增产综合技术的核心应从畜水、保水、节水和高效用水出发来提高蔗田水分（自然降水、补充灌水）利用效率；并提出了“提高蔗田蓄水能力，降低土壤水分蒸发，充分有效利用现有水资源和开源节流”四大环节组成的抗旱增产的综合技术体系及其对甘蔗增产的重要作用。

长江上游特旱特涝年夏季风特征的分析

本文采用700百帕、500百帕上的假相当位温θse和温度露点差(t—td)的候平均演变曲线,反映出长江上游地区夏季风的变化,并对比分析了长江上游特旱的1972年和特涝的1974年的夏季风活动规律,表明干旱年受夏季风影响的时间短于洪涝年。通过500百帕上的候平均θse值,构造了一个表征当年夏季风特征的夏季风的综合指数Icsm,分析结果表明,该指数能反映出夏季风到达迟早、持续时间及强度等特征,为长江上游的旱涝预报提供了一个依据。

特旱条件下玉米自交系抗旱性探讨

在我国现代社会中,农业的发展情况关系到我国人民群众的生活水平。我国的玉米种植行业一直在致力于开发玉米的新品种,通过玉米自交实验以及杂交实验来培育出抗旱能力强并且产量高的玉米品种,由于我国的地理环境以及气候特点,玉米种子的品种必须要求有一定的抗旱能力,相关的玉米种子研究人员做了玉米生育全期的控水实验,研究了58种玉米自交种子的抗旱性能,并对各个玉米自交系作出了其抗旱性能的客观评价。本文针对于特旱条件下玉米自交系统抗旱性进行了探讨。

厦门市2002年春季特旱分析

本文分析厦门市2002年春季特旱的主要特征，与近百年来厦门市春季特旱年例作了对比。从天气气候的角度和大尺度环流背景分析，表明厦门春季特旱的主要成因是：西太平洋副热带高压，特别是南海高压长时期面积偏大、强度偏强；印缅槽偏弱；亚洲地区盛行纬向环流。

湖南特大干旱时空变化特征分析

利用湖南建站以来至2014年97个国家气象观测站的逐日气温、降水、相对湿度等观测资料计算逐日气象干旱综合指数,运用线性倾向估计方法,统计分析湖南特大干旱的时空变化特征。结果表明:全省特旱影响范围总体扩大,年际变化呈显著上升趋势。特旱年际变化倾向率总体呈上升趋势,平均值为0.016次·a-1,其中衡邵地区上升最快,湘东北下降最快。整体下半年比上半年更易发生特旱,10月特旱频次最多。桑植、宁乡、怀化、郴州、邵东5个代表站最长干旱持续日数越多,特旱发生概率越大,特旱均发生在最长干旱持续日数20 d以上的年份,且多年连续特旱明显多于单独某一年特旱。各代表站最长干旱持续日数出现频次夏季最高,春季最少,跨季节的连旱一般跨越两个季节,夏秋连旱出现频次最高,个别年份跨越3个季节。

特早熟玉米叶片生长规律探讨

对三种植株密度、三种氮肥水平条件下特早熟玉米出叶速度的生长规律进行了研究,结果表明:特早熟玉米出叶速度主要受品种特性影响;三种密度下的出叶速度相差不大;三种氮肥水平下450 kg.hm-2的处理其出叶速度最快。特早熟玉米的出叶速度表现为上部和基部较快,中部较慢。试验表明:6万株.hm-2和450 kg.hm-2的组合是比较合适的组合,有利于特早熟玉米叶片的生长。

新宁脐橙的气候灾害特征分析

利用新宁国家基本气象观测站1960~2020年观测气象资料及新宁农业农村局2016~2020年脐橙数据,对新宁脐橙的气候适应性进行了研究。发现1960~2020年新宁平均每年出现干旱2.9次,其中轻旱平均每年1.3次,中旱1.1次,重旱0.4站;重旱出现的主要时段为1962~1973年、1988~2000年、2007~2020年,重旱呈下降的趋势,倾向率为−0.05次/10a。特旱的趋势与重旱相反,呈上升的趋势,倾向率为0.01次/10a。重旱和特旱主要出现在秋季。而脐橙的成熟期为11~12月,因此对脐橙的产量影响很大。新宁县的平均气温、平均最高气温和平均最低气温总体均呈上升趋势。从温度积温变化趋势来看,新宁将更加适宜种植脐橙。

果树栽植要重“五特”

一、特旱 要注重发展成熟期特别早的果树或某类果树中成熟特别早的品种。前几年,苹果中,晚熟品种发展过多,而早熟品种被人忽视,结果造成一些老牌早熟品种仍有良好的市场前景。此外,除在树种、品种选择上下功夫外,还可以从反季节栽培方面做文章。谁不愿品尝早春第一果泥?只要抓住“早”宇,就可能获得可观的经济利益。

Grey Correlation Analysis of Physiological Traits Related to Drought Tolerance in Pennisetum sp.

The drought resistance of Pennisetum sp. was analyzed under different drought stress conditions simulated by various concentrations of PEG-6000. Changesofa series of indexes such as chlorophyll content, water content, relative electrical conductivity of osmotic solution, MDA content, proline content, soluble polysaccharide content and soluble protein content in the leaves were measured.The correlation of these indexes with the drought resistance of Pennisetum sp. was an- alyzed by the method of grey correlation analysis. The results showed that the chlorophyll, water content, relative electrical conductivity and soluble protein con- tentexhibited obvious negative correlation with the stress concentration, which de- creasedfollowing the increase of PEG-6000 concentration. The soluble polysaccha- ride contentshowed an increasing trend,the MDA content showed a rise at first fol- lowed by a declinetrend, while the prolinecontent was just opposite to MDA. The changes of the 3 indexes showed obvious positive correlation with thestress con- centration. The correlation of these indexes with the drought resistance of Pennise- tum sp. were ranked as follows： leaf water content （0.980 8）, chlorophyll content （0.967 9）, MDA content （0.876 0）, soluble polysaccharide content （0.839 5）, soluble protein content（0.827 5）, relative electrical conductivity of osmotic solution（0.670 8）, and proline content（0.571 3）.

Effects of Water Stress on Photosynthesis and Fluorescence Characteristics in Peony

[ Objective] Study on the photosynthesis and fluorescence characteristics in peony under water stress. [ Method ] The two peony varieties Huhong and Luoyanghong were treated by different water stress for determining the photosynthesis and fluorescence characteristics. [ Result ] With the aggravation of water stress, the net photosynthetic rate （Pn） and stomatal conductance （Gs） decreased, while the intercellular CO2 concentration （Ci） increased. Drought could decrease Pn, constrain gas exchange and change the daily photosynthesis. Fo of peony leaf increased and Fv/Fm decreased under water stress especially water logging, causing the inactivation of the PS II reaction center, and the chlorophyll fluorescence characters gradually recovered until afternoon. [ Conclusion] The 75% soil relative water content （SRWC） is the best condition for growth of peony. Compared with drought, water logging is more unfit for the growth of peony. For the two varieties, Huhong assumed more tolerance to drought, accordingly more adaptability.

Analysis of Antioxidant Characteristics in Seedling Roots of Sweetpotato(Ipomoea batatas(L.) Lam.) with Different Drought Tolerance under Simulated Drought Stress

[Objective] Jishu 21 with strong drought tolerance and Jizishu 1 with weak drought tolerance were chosen to reveal antioxidant characteristics in seedling roots of sweetpotato with different drought tolerance. [Method] Active oxygen, antioxidant substances and antioxidant enzymes in seedling roots of sweetpotato with different drought tolerance were analyzed by hydroponics with PEG-6000 for simulating drought stress in the experiment. [Result] The results showed that under drought stress, H202 content and formation rate of 02_ in seedling roots of Jizishul were higher than Jishu 21 by 1.9% and 102.6%, respectively, the contents of Vc in seed- ing roots of Jizishu 1 and Jizishu 1 increased by 25.3% and 81.1%, respectively, and the contents of polyphenols increased by 24.8% and 37.6% in the two vari- eties, respectively. The increase amplitudes of Jizishu 1 were higher than Jishu 21 in the above indexes. Antioxidant enzyme activities were higher in seedling roots of Jisl^u 21 and Jizishul under drought stress than normal treatments; and among them, POD activity was the highest, while PPO activity was the lowest in all an- tioxidant enzymes. The increases of SOD, POD, APX and PPO activities in Jishu 21 were twice of those in Jizishul. The bands of SOD3, POD2, CAT1, APX2 and PPO2 changed obviously between the drought treatments of the two varieties. [Con- clusion] In conclusion, stronger drought tolerance in sweetpotato results in lower in- crease amplitudes of H202 content, formation rate of 02- and contents of Vc and polyphenols under drought stress, and the activities of antioxidant enzymes are stronger in seeding roots under drought stress; and the differences in antioxidant enzymes are mainly related to the changes of isoenzymes including SOD3, POD2, CAT1. APX2 and PPO2.

Analysis on the Hydrochemical Characteristics of Groundwater and the Formation Reason in Wadi Bay Area of Libya

[Objective] The research aimed to analyze the formation reason of groundwater hydrochemical characteristics in the dry valley area of Wadi Bay of Libya and provide the scientific basis for the reasonable development utilization and the environmental protection of groundwater.[Method] Took Wadi Bay area（dry valley）of Libya as the example,Piper trilinear graphic representation method,the descriptive statistics,the ion ratio coefficient method and the isotope evidence were used to systematically study the special hydrochemical characteristics of shallow groundwater in the arid climate condition in Wadi Bay area of Libya.[Result] The salt content of groundwater in the area was very high,and TDS was during 3.2-8.4 g/L.The main groundwater type was Cl·SO4-Na·Ca,then was Cl·SO4-Na·Ca·Mg.The concentrations of Cl-,Na＋ and SO2-4,etc.in the groundwater in 70 km from the sea had the remarkable variation,but the concentrations of Mn2＋,Ba2＋,Si2＋,NH＋4 and NO-3 didn＇t have the same variation phenomenon.[Conclusion] The hydrochemical characteristics of shallow groundwater didn＇t relate to the dissolution infiltration reaction,the evaporation concentration effect and human activities.The major cause was the mixing effect of salt and fresh water in the invasion process of seawater.

Modeling habitat suitability of range plant species using random forest method in arid mountainous rangelands

Mountainous rangelands play a pivotal role in providing forage resources for livestock, particularly in summer, and maintaining ecological balance. This study aimed to identify environmental variables affecting range plant species distribution, ecological analysis of the relationship between these variables and the distribution of plants, and to model and map the plant habitats suitability by the Random Forest Method(RFM) in rangelands of the Taftan Mountain, Sistan and Baluchestan Province, southeastern Iran. In order to determine the environmental variables and estimate the potential distribution of plant species, the presence points of plants were recorded by using systematic random sampling method(90 points of presence) and soils were sampled in 5 habitats by random method in 0–30 and 30–60 cm depths. The layers of environmental variables were prepared using the Kriging interpolation method and Geographic Information System facilities. The distribution of the plant habitats was finally modelled and mapped by the RFM. Continuous maps of the habitat suitability were converted to binary maps using Youden Index(?) in order to evaluate the accuracy of the RFM in estimation of the distribution of species potentialhabitat. Based on the values of the area under curve(AUC) statistics, accuracy of predictive models of all habitats was in good level. Investigating the agreement between the predicted map, generated by each model, and actual maps, generated from fieldmeasured data, of the plant habitats, was at a high level for all habitats, except for Amygdalus scoparia habitat. This study concluded that the RFM is a robust model to analyze the relationships between the distribution of plant species and environmental variables as well as to prepare potential distribution maps of plant habitats that are of higher priority for conservation on the local scale in arid mountainous rangelands.

Daily SPEI Reveals Long-term Change in Drought Characteristics in Southwest China

Drought is the most widespread and insidious natural hazard, presenting serious challenges to ecosystems and human society. The daily Standardized Precipitation Evapotranspiration Index(SPEI) has been developed to identify the regional spatiotemporal characteristics of drought conditions from 1960 to 2016, revealing the variability in drought characteristics across Southwest China. Daily data from142 meteorological stations across the region were used to calculate the daily SPEI at the annual and seasonal time scale. The Mann-Kendall test and the trend statistics were then applied to quantify the significance of drought trends, with the following results. 1) The regionally averaged intensity and duration of all-drought and severe drought showed increasing trends, while the intensity and duration of extreme drought exhibited decreasing trends. 2) Mixed(increasing/decreasing) trends were detected, in terms of intensity and duration, in the three types of drought events. In general, no evidence of significant trends(P < 0.05) was detected in the drought intensity and duration over the last 55 years at the annual timescale. Seasonally, spring was characterized by a severe drought trend for all drought and severe drought conditions, while extreme drought events in spring and summer were very severe. All drought intensities and durations showed an increasing trend across most regions, except in the northwestern parts of Sichuan Province. However, the areal extent of regions suffering increasing trends in severe and extreme drought became relatively smaller. 3) We identified the following drought hotspots: Guangxi Zhuang Autonomous Region from the 1960 s to the 1990 s, respectively. Guangxi Zhuang Autonomous Region and Guizhou Province in the 1970 s and 1980 s, and Yunnan Province in the 2000 s. Finally, this paper can benefit operational drought characterization with a day-to-day drought monitoring index, enabling a more risk-based drought management strategy in the context of global warming.

Symbiotic and Phenotypic Characteristics of Rhizobia Nodulaing Cowpea （Vigna Unguiculata L. Walp） Grown in Arid Region of Libya （Fezzan）

Symbiotic and phenotypic characteristics of thirty rhiobial isolates obtained from root nodules of two cowpea （Vigna unguiculata L. Walp） cultivars that grown in different sites of Fezzan （Southern part of Libya） were studied. Cultural characteristics and cross-nodulation with Arachis hypogega and Faidherbia albida showed that they were slow-growing rhizobia. Each isolate was found to coexist with non-symbiotic bacteria similar in their cultural characteristics to fast-growing rhizobia. All isolates formed symbiosis with the test plants, but different in their nitrogen-fixation efficiency. Numerical analysis of phenotypic characteristics showed that at boundary level of 70% average similarity, the isolates formed four distinguished groups and two isolates remained separate. Most isolates exhibited wide tolerance to acidity, alkalinity and extreme temperatures. They also resistant to some heavy metals such as mercury, copper, zinc, lead, cadmium and aluminum at low concentrations and antibiotics like polymyxin, colistin, bacitracin and nalidixic acid. Isolates displayed different response to salinity ranging from sensitive, which unable to grow in 1% NaCI to resistant and grow at 2% NaCl or above. Urea was hydrolyzed by most of them and carbohydrates utilizations were different. Sucrose and maltose were metabolized by most of the test isolates, whereas, monosaccharide and sugar alcohols were poorly utilized.

Characteristics of Drought and Humidification Based on Standardized Precipitation Index in Weifang City during the Past 50 Years

[Objective] This study aimed to analyze the evolution characteristics and occurrence patterns of droughts and floods in Weifang City. [Method] Based on the monthly precipitation data during 1961-2010 obtained from nine meteorological sta- tions of Weifang City, by using standardized precipitation index, monthly SPI index of Weifang City during the past 50 years was calculated to analyze the spatial and temporal distribution characteristics of drought and humidification in Weifang City. [Result] The results showed that the variation of drought and humidification had stage characteristics in Weifang City, which was relatively humid in the 1960s and 1970s and developed from extremely humid in early 1960s to dry in late 1970s, persistent drought was observed throughout the range of Weifang City in the 1980s, and the variation tended to be smooth during the 1990s-2000s. Spatial distribution of drought and humidification in Weifang City showed certain regional characteristics. In the 1960s, the mid-west region of Weifang City was relatively humid, while the southeastern region was relatively dry; in the 1970s, there was little difference among the drought and humidification extent in each region; in the 1980s, each region of Weifang City was generally dry, specifically, drought in the southeastern region was the most severe, while drought in the northern region was the slightest; in the 1990s and 2000s, variation of drought and humidification in each region of Weifang City was basically the same. The uneven spatial and temporal distribution of precipi- tation led to abnormal distribution of drought and humidification in some areas, such as the abnormal phenomenon in 1999; the spatial distribution of drought and humidi- fication duration in each generation had their own characteristics, which brought diffi- culties to the unified deployment of drought and flood control departments. [Conclu- sion] This study provided theoretical basis for the drought resistance, waterlogging prevention and disaster reduction in Weifang City under the background of climate change.

Drought Resistance of Slope Pioneer Plant Magnolia multiflora

[Objective] This study aimed to reveal responses of Magnolia multiflora to soil drought stress. [Method] Pot experiment was employed to simulate drought stress, and photosynthetic and physiological indices of M. multiflora were determined. [Result] The net photosynthetic rate （Pn） of M. multiflora did not change significantly under mild drought stress, and reduced significantly under moderate and severe drought stress. Drought stress reduced stomatal conductance （Gs）, transpiration rate （Tr） and intercellular CO2 concentration （Ci）, and compared with those in the control group, the Pn, Gs, Tr and Ci under severe drought stress declined by 61.04%, 86.27%, 87.77% and 42.63%, respectively. The malondialdehyde （MDA） content in M. multiflora leaves did not increase significantly under mild drought stress, and increased significantly under moderate and severe drought stress. The MDA content in M. multiflora leaves under severe drought stress was 1.63 times as high as that in the control group. The proline （Pro） and soluble sugar contents of M. multiflora increased significantly with the aggravation of drought stress, and those under severe drought stress were 8.06 times and 3.16 times respectively higher than those in the control group. [Conclusion] M. multiflora has a strong drought tolerance, and is suitable for growing in relatively arid environment. It can be used as candidate for vegetation restoration in hydropower engineering slope.